A motor vehicle may employ a single or multiple power-sources. Such vehicles can either employ a powertrain where internal combustion engine(s) are used to propel the vehicle, or a hybrid powertrain, where two or more distinct power-sources, are used to accomplish the same task. In a wheeled motor vehicle having multiple power-sources, the individual power-sources can be used to power different wheels.
In such a hybrid powertrain, an internal combustion engine can be used as the main power-source and an electric motor can be used as an auxiliary power-source. To maximize fuel efficiency of such a powertrain, at least one of the power-sources may be shut off when little or no powertrain torque is required for driving the vehicle. Such a situation may be encountered when the subject vehicle is maintaining a steady cruising speed, is in a coast down mode, i.e., when the vehicle is decelerating from elevated speeds, or the vehicle is stopped.
Also, the auxiliary power-source, such as the electric motor, can be operated in addition to the main power-source, such as the internal combustion engine, to selectively maximize output of the powertrain when such increased output can be used effectively to power the vehicle. In other words, the auxiliary power-source can be used to selectively augment power generated by main power-source to boost acceleration of the vehicle when warranted by the presence of such limiting factors as g-forces acting on the vehicle and road conditions or wheel traction.